[Discussion] Easing the learning curve for introducing generic parameters

[benrimmington]

The any MyProtocol syntax may not be possible, due to the global any(_:) function:

@John_McCall

The Core Team also considered that this use of any and all will likely prevent their future use as keywords. However, claiming these identifiers as keywords would already cause problems with a fair amount of existing code, and it's far from clear that these would be the best choices for keywords in any event.

Any & MyProtocol is already permitted, so could this be a backwards-compatible syntax for existential types? The compiler might generate a warning and fix-it in Swift 5.x, followed by an error in Swift 6 or later?

However, MemoryLayout<Any & MyProtocol>.size doesn't compile in Swift 5.5 — a workaround is to use a typealias of the protocol composition.